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Re: Blank nodes & classes

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Thu, 21 Jun 2007 11:10:30 +0100
Message-ID: <640dd5060706210310s52a69f8bq211e2133218d5929@mail.gmail.com>
To: "Ben Adida" <ben@adida.net>
Cc: "CÚdric Mesnage" <cedric.mesnage@lu.unisi.ch>, public-rdf-in-xhtml-tf@w3.org

Hi Ben/CÚdric,

[I'm not proposing a resolution to this question in this version of
RDFa, but I think it's useful to collect use-cases.]

I had a use-case the other day that is related to the ones you are
describing. Essentially the question we all seem to be converging on
is what is the minimum amount of mark-up that should give us a triple?

So, the following feels quite natural, as a way of marking up the
mention of something like a book in my blog:

  Today I bought a copy of
  <span about="urn:ISBN:0091808189" class="bib:book">
    Canteen Cuisine
  </span>
  from my local bookshop.

Since my system uses the URI to retrieve some data about the book from
a book site like Amazon, I don't actually need any further triples
like title, price, publisher, author, or whatever. But there is a an
interesting question as to whether the following should be enough to
get an entry in the triple store:

  <span about="urn:ISBN:0091808189">
    Canteen Cuisine
  </span>

The system could still do the same thing, and retrieve additional
triples based on the resource, but the question is what are the
parsing rules that get from this mark-up to a triple?

The only way I can think of to achieve this from the mark-up I've
shown is be automatically generate labels from the content of
elements. The mark-up would therefore generate this:

  <urn:ISBN:0091808189> rdfs:label "Canteen Cuisine" .

and we would now have the URI for the book in our triple-store, and
can make use of it to retrieve further information.

Regards,

Mark

On 13/06/07, Ben Adida <ben@adida.net> wrote:
>
>
> Cedric,
>
> This is an interesting question. I had to deal with this with the RDFa
> clipboard [1], and I chose to use the predicate rel="rdf:li" on any
> bnode I wanted to appear on the page, effectively saying "this bnode is
> an item of the current page." For example, in your code below:
>
> <span class="foaf:Person" rel="rdf:li">
> some things about the person
> </span>
>
> which yields:
>
> <> rdf:li
>      [a foaf:Person; ...things about the person...]
>
> I'm pretty sure this is not a "best practice", but it's the work-around
> I came up with for precisely this issue, and it's not all that wrong in
> terms of semantics: after all, that *is* an item on the page.
>
> -Ben
>
> CÚdric Mesnage wrote:
> > Hi all,
> >
> > I have a question regarding blank nodes in RDFa, I don't know if the
> > issue has been raised already and I apologize if it has. In the RDFa
> > Primer I saw that you can create unnamed blank nodes using the 'rel'
> > attribute as in the example:
> >
> > <dl class="foaf:Person" about="#card" id="card">
> > ...
> >  <dt>Address</dt>
> >  <dd rel="foaf:address">
> >   <span property="foaf:address_line_1">77 Massachusetts Ave.</span><br />
> >     <span property="foaf:address_line_2">MIT Room 32-G524</span><br />
> >   <span property="foaf:city">Cambridge</span> MA 02139<br />
> >   <span property="foaf:country">USA</span>
> >  </dd>
> > ...
> > </dl>
> >
> > This works for predicates layered in an instance definition, do you plan
> > having a similar principle for classes? I'd like to have:
> >
> > <span class="foaf:Person" >
> > some things about the person
> > </span>
> >
> > to be considered as a blank node, currently in RDFa On
> > Rails(http://rdfa.rubyforge.org/) I generate blank node names this way:
> >
> > <span class="foaf:Person" about="#BNode1">
> > some things about the person
> > </span>
> >
> > incrementing the number through the page generation, but this is ugly.
> > The other solution is that I can just forbidden the use of classes if no
> > uri or explicit blank node name is given.
> >
> > Hope this does make some sense and look forward to get you point of view.
> >
> > Best Regards!
> > ---
> > CÚdric Mesnage
> > PhD Student
> > cedric.mesnage@lu.unisi.ch <mailto:cedric.mesnage@lu.unisi.ch>
> > http://www.inf.unisi.ch/phd/mesnage/
> > http://myunderstanding.wordpress.com/
> >
> >
>
>
>
>


-- 
  Mark Birbeck, formsPlayer

  mark.birbeck@x-port.net | +44 (0) 20 7689 9232
  http://www.formsPlayer.com | http://internet-apps.blogspot.com

  standards. innovation.
Received on Thursday, 21 June 2007 10:10:34 UTC

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